This invention relates to rolling and more in particular to a roll-forging mill.
The invention is readily applicable for use in a combined continuous-casting and rolling plant where the casting and rolling operations are carried out in a single continuous technological process.
To ensure reliable and effective operation of such combined continuous-casting and rolling plant, it is necessary to eliminate axial stress in the strained metal. Axial stresses are due to occur in the metal being worked at a rolling mill as a result of interaction between the mill workrolls and the metal. The axial stress from the rolling mill is transmitted through the metal to the mould of a continuous casting machine, thereby causing idling periods in the operation of a continuous-casting and rolling plant.
To ensure effective combined operation of a continuous casting machine and a rolling mill, it is important to meet the following requirement: notwithstanding its small weight, the rolling mill should be capable of performing substantial amount of reduction in a single pass.
Therefore, the two aforementioned conditions are necessary for effective operation of a combined continuous-casting and rolling plant.
The first condition can be met by providing a single technological process wherein a continuous casting machine is used together with a conventional two-high mill incorporating grooved rolls, for example, such as described in Austrian Pat. No. 280,191. By varying the speed of rotation of the workrolls, the speed of casting is made equal to that of rolling, whereby axial stress is eliminated in the metal being worked. However, the amount of metal reduction in this case is small due to the overfilling of the roll pass.
An increase in the number of two-high mills (the installation of a continuous mill) with the purpose of enhancing the total amount of reduction will invariably lead to an increase in the mass of such rolling mills, which have been found inefficient due to the impossibility of eliminating axial stress in the strained metal. The difficulty here is to coordinate the speeds of rolling in the mill stands.
The problem of combining the continuous casting process with that of rolling is possible to solve by making use of a roll-forging mill, which is capable, at its small weight, of performing rolling of the continuous-cast ingot with a substantial amount of reduction per pass.
The roll-forging mill mentioned above comprises a power driven roll stand mounted on a frame for reciprocation along the passline and provided with working tools, such a strikers, which perform rocking motion through the intermediary of bars articulated on a support stand. The support stand and the roll stand actuator are rigidly secured on the frame.
As the roll stand advances, the strikers perform pendulum-like motion under the action of the bars, thereby effecting reduction of metal along the rolling cone. Reduction of metal is effected in a single pass during forward movement of the roll stand, whereupon a successive portion of metal is fed for rolling by means of a feeding and clamping mechanism during the return idle movement of the roll stand. The feeding mechanism is positioned at the side of the metal entry into the roll stand and the clamping mechanism at the exit therefrom.
In the course of operation of the above-described mill, axial stresses are due to occur in the metal being worked because of fixed positions of the support stand and of the roll stand actuator.
In the process of rolling effected at such mill the metal remains immobile at a moment of reduction, whereas the billet produced at a continuous-casting machine remains in continuous motion. Therefore, axial stresses in the metal under strain are unavoidable in the combined continuous-casting and rolling processes. Needless to say that the presence of axial stresses in the metal being worked is too serious a flaw to be disregarded.
What is required is a roll-forging mill of the type permitting the elimination of axial stresses due to occur in the strained metal during its reduction. Working tools in such mill are permitted to operate in synchronism and the mill per se is made more simple in construction and easy in operation.